What causes "no such group: " in geektutu/7days-golang?

Call geecache.NewGroup with the exact name on every node in the pool.

no such group:

Error message

no such group:

What it means

HTTP 404 response in HTTPPool.ServeHTTP: the group name extracted from the URL path /<basepath>/<groupname>/<key> is not registered via GetGroup, so no cache group exists under that name. It fires for peer requests naming a group this node does not host.

Source

Thrown at gee-cache/day4-consistent-hash/geecache/http.go:50

// ServeHTTP handle all http requests
func (p *HTTPPool) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if !strings.HasPrefix(r.URL.Path, p.basePath) {
		panic("HTTPPool serving unexpected path: " + r.URL.Path)
	}
	p.Log("%s %s", r.Method, r.URL.Path)
	// /<basepath>/<groupname>/<key> required
	parts := strings.SplitN(r.URL.Path[len(p.basePath):], "/", 2)
	if len(parts) != 2 {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}

	groupName := parts[0]
	key := parts[1]

	group := GetGroup(groupName)
	if group == nil {
		http.Error(w, "no such group: "+groupName, http.StatusNotFound)
		return
	}

	view, err := group.Get(key)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/octet-stream")
	w.Write(view.ByteSlice())
}

View on GitHub (pinned to cf36443821)

Solutions

Call geecache.NewGroup with the exact name on every node in the pool.
Match the URL group name case-sensitively against the NewGroup registration.
Share a single group-registration bootstrap (config-driven) across all peers to avoid drift.
Log registered group names at startup to spot naming drift early.

Example fix

// before: node never registers the group
// (no NewGroup call) -> 404
// after: register in each node's startup
geecache.NewGroup("scores", 2<<30, geecache.GetterFunc(loadScores))

Defensive patterns

Strategy: validation

Validate before calling

// day4: verify group registration on this node before remote reads
if geecache.GetGroup("scores") == nil {
    geecache.NewGroup("scores", 2<<30, geecache.GetterFunc(loadScores))
}

Try / catch

// Go: distinguish 404 (group missing) from other failures
if resp.StatusCode == http.StatusNotFound {
    return fmt.Errorf("group not registered on peer %s", peerAddr)
}

Prevention

Register identical groups on every node of the consistent-hash cluster.
Drive group names from shared config, not per-node literals.
Fail fast at startup if any configured group is missing via GetGroup.
Alert on 404s from cache peers — they indicate deployment drift, not user error.

When it happens

Trigger: GET /_geecache/<unknownGroup>/<key>; group name mismatch between URL and NewGroup; group registered on one peer but not this one.

Common situations: Group-name typos; inconsistent bootstrap across a consistent-hash cluster; deploying new nodes that lack the group registration code path.

Related errors

AI-assisted analysis of geektutu/7days-golang@cf36443821 (2026-09-03). Data as JSON: /api/errors/1b4df39e55663583. Report an issue: GitHub.